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Guarded Free — CodeQL query help documentation

ID: cpp/guarded-free
Kind: problem
Security severity: 
Severity: recommendation
Precision: very-high
Tags:
   - maintainability
   - readability
Query suites:
   - cpp-security-and-quality.qls

Click to see the query in the CodeQL repository

The free function, which deallocates heap memory, may accept a NULL pointer and take no action. Therefore, it is unnecessary to check the argument for the value of NULL before a function call to free. As such, these guards may hinder performance and readability.

Recommendation

A function call to free should not depend upon the value of its argument. Delete the condition preceding a function call to free when its only purpose is to check the value of the pointer to be freed.

Example

void test()
{
    char *foo = malloc(100);

    // BAD
    if (foo)          
        free(foo);

    // GOOD
    free(foo);
}

In this example, the condition checking the value of foo can be deleted.

References